Mortise and tenon joints and dovetail joints for joining the ends of wooden boards together were originally cut by hand using saw and chisel. Routed joints made with a hand held router are used today and try to duplicate this type of hand joinery.
The only true mechanical routed interlocking joint is a dovetail joint and in common forms of through dovetail, half blind dovetail and sliding dovetail are all routed on different types of templates with a tapered or dovetail cutter. In one embodiment a full blind dovetail is made with a router as described in U.S. Pat. No. 4,025,215.
All of these joints are formed using a router with either a dovetail cutter alone or with a dovetail cutter on one element and a straight sided cutter on the other. There is no mechanically interlocking joint and no means of forming a mechanically interlocking joint using a router with only a straight sided cutter on both halves of the joint.